This invention relates generally to crop harvesting and threshing machines, more commonly known as combines, and more particularly to a sensing bar or plate mounted in the infeed housing that is attached to the front of the base unit of the combine. The sensing bar is used to detect stones or other non-frangible objects which are transferred to the infeed housing with crop material from the harvesting attachment or header before such objects are conveyed upwards into the base unit where the threshing operation occurs. Specifically, the invention is concerned with the shape of the contacting surface of the sensing bar and the acoustical isolation means employed to maximize the number of impactions of stones and other non-frangible objects with the bar, increase the sensitivity of the bar to such impactions and decrease the amount of noise transmitted via the infeed housing from the header and the combine to the sensing bar during operation. The net effect of this cooperative interaction between the shape of the sensing bar and the acoustical isolation means is, sequentially, the successful detection by a stone and non-frangible object detecting apparatus and the ejection from the infeed housing of such an object by object ejecting apparatus.
In the prior conventional types of combines, stone traps were routinely provided to separate out large hard objects or stones that generally were greater than three or four inches in size. The stone traps provided in the conventional combines were utilized generally in two types of stone ejecting systems. The passive type of stone ejecting system employed a stone trap with a space or gap between the top of the crop elevator or conveyor within the infeed housing and the base unit threshing apparatus. In this type of an ejecting system hard objects or stones were conveyed upwardly along with the crop material from the header through the infeed housing towards the threshing apparatus. When the crop material passed over the gap, stones by their very weight would fall down through the gap into the stone trap. Those stones that were carried along with the crop material past the stone trap were passed into contact with the threshing cylinder, which generally was rotatably mounted transversely to the longitudinal axis of the combine. If the hard objects or stones were of sufficient size so that they would not easily pass between the threshing cylinder and the threshing concaves, they would be thrown backwardly by the rotation of the cylinder into the gap or space. Thus, this particular cooperation between the threshing cylinder and the stone trap created an almost natural stone ejecting system for conventional combines. Even if a stone did pass into the threshing cylinder it made only one pass about the cylinder and across the underlying concave, usually doing minimal damage to the threshing apparatus before it was passed on through and ejected from the combine.
The second type of stone ejecting system generally employed an active system which utilized some sort of a detecting system to detect the presence of a stone or other non-frangible object. Typically an electronic sensor, such as an acoustic transducer usually in the form of a piezoelectric disc, is mounted in a sensing plate and is used in conjunction with a stone trap. The electronic sensor responded to the characteristics of the sound, such as the amplitude and frequency, that an impacting stone generated in the sensing bar. This signal would then be transferred through an electronic circuit that filtered out the range within which the amplitude and frequency was characteristic of stones. Within this characteristic spectral range the electronic circuit automatically activated a latch releasing mechanism on a door along the bottom of the infeed housing that would pivot open to permit the stones or hard objects to be ejected from the infeed housing along with a small amount of crop material.
This latter or active type of sensing system utilizing a latched trap door that was automatically opened upon impact of a rock or hard object against the sensing bar was an appreciable step forward in stone detecting and ejecting technology. However, because the stones or hard objects were generally passed along the predetermined path of travel with the crop material, it was possible for a stone or other hard object to pass over the sensing bar with the crop material without striking the bar. Then the undetected stones or hard objects would still pass upwardly through the infeed housing into the threshing apparatus, where they would pass with the crop material about the threshing concave and the threshing cylinder. Again, because it was only a single pass of crop material about a portion of the conventional transverse threshing cylinder and across a relatively narrow strip of concave, the undetected and therefore unejected stones still caused minimal damage to the combine.
An alternate type of active stone ejecting system utilized a pinch roll rotatably mounted in the infeed housing at a predetermined distance above the trap door. When a stone of sufficient size was carried by the crop elevator between the pinch roll and the trap door into compressive engagement therewith, the rotation of the pinch roll exerted a downward force through the stone against the trap door. The trap door was spring loaded closed so that above a predetermined pressure the door would be forced open, thereby causing the stone to be directed downwardly and out of the infeed housing through the opening created by the opened trap door. An obvious drawback to this system was the fact that large, but relatively flat stones or hard objects capable of passing between the pinch roll and the trap door were ingested into the combine where they could still damage the operating components.
The advent of rotary or axial flow type of combines with single or multiple threshing and separating rotors utilized in an orientation where the longitudinal axis of each rotor is either parallel or transverse to the longitudinal axis of the combine presented a greater need for more effective stone eliminating or ejecting systems. This increased need stems from two principal facts. Axial flow combines generally do not have a transverse threshing cylinder at the top of the infeed housing to throw or direct stones or other damage inducing objects back into the stone trap. They also pass the crop material about the periphery of each rotor as many as five or six times during threshing and separation as the crop material progresses axially along the length of each rotor.
An improved electronic stone or hard object detecting system was developed, as shown and described in copending U.S. patent application Ser. No. 109,932, filed Jan. 4, 1980 and assigned to the assignee of the present invention, utilizing a sensing bar that is positioned transversely across the bottom of the infeed housing astride the path of crop flow from the header to the base unit of the combine. In this type of a system the reaction time for the opening of the trap door is relatively short and, because the crop material in an axial flow combine makes multiple passes about the rotor as it is transferred along the length of the concave during the threshing and separating cycle, the detection and subsequent elimination of detected stones and hard objects becomes more critical. A stone or other non-frangible object passing through an axial flow type of combine is more apt to damage the entire length of the concaves, which with their rasp or rub bar cooperate with the rotors to thresh the crop material. In marked contrast, a stone passing through a conventional type of combine with a transversely oriented threshing cylinder and underlying concave contacts only a very small portion of the concave and is therefore likely to cause relatively little damage in its single pass about a portion of the cylinder. Thus, any improvements to the detecting system would enhance the effectiveness of the overall ejecting system. Particularly, increasing the percentage of objects striking the sensor bar will enhance the effectiveness.
Additionally, the ejecting system disclosed in the aforementioned copending patent application employes a sensing system that is shock mounted on rubber mounts to reduce the interfering noise transmitted to the sensing bar that routinely is generated by the moving parts of the header, infeed housing and combine during operation. This system of mounting the bar suffers from the serious disadvantage of permitting relatively large amounts of crop material to escape between the sensing bar and the bottom surface of the infeed housing where there is a sizable gap.
The foregoing problems are solved in the design of the sensing bar comprising the present invention by providing an improved sensing bar design that incorporates an inclined section into the bar to increase the percentage of impactions likely to occur by rocks and other non-frangible objects thereagainst as they are transported upwardly through the infeed housing. The sensing bar is also mounted to the floor bottom surface of the infeed housing in an improved acoustically isolating manner to decrease the noise level to which the sensing bar will be subjected during operation and reduce the quantity of crop material that is lost from the infeed housing at the junction of the sensing bar and the infeed housing floor.